1. Field
Exemplary embodiments of the present invention relate to an address detection circuit and a memory device.
2. Description of the Related Art
A memory cell of a memory device includes a transistor operating as a switch and a capacitor which stores a charge, which corresponds to data. The data is divided into ‘High’ (logic 1) or ‘Low’ (logic 0) depending on whether a charge is present in the capacitor of the memory cell, that is, whether the terminal of the capacitor has a high voltage level.
In principle, the retention of data does not consume power because data is retained as an accumulated charge in the capacitor. However, data may be lost as the initial amount of charge stored in the capacitor is reduced due to current leakage in the PN junction of the MOS transistor. In order to prevent this concern, data within a memory cell needs to be read before the data is lost and capacitor needs to be recharged. Such an operation must be periodically repeated to maintain the data. The process of recharging cells is referred to as a refresh operation.
FIG. 1 is a diagram showing part of a cell array in a memory device which will be used to describe a word line disturbance phenomenon. In FIG. 1, BL0 and BL1 denote bit lines.
In FIG. 1, WLK−1, WLK, and WLK+1 denote word lines arranged in parallel in the cell array. The word line WLK indicated by HIGH_ACT is a highly active word line (or a frequently activated word line) that has a high activation number (or frequency), and the word lines WLK−1 and WLK+1 are adjacent to the word line WLK. CELL_K−1, CELL_K, and CELL_K+1 denote memory cells coupled to the respective word lines WLK−1, WLK, and WLK+1. The memory cells CELL_K−1, CELL_K, and CELL_K+1 include cell transistors TR_K−1, TR_K, and TR_K+1 and cell capacitors CAP_K−1, CAP_K, and CAP_K+1, respectively.
In FIG. 1, when the word line WLK becomes active and precharged (or deactivated), the amount of charge stored in the cell capacitors CAP_K−1 and CAP_K+1 is influenced by the rise and fall of voltages at word lines WLK−1 and WLK+1 due to a coupling phenomenon generated between the word line WLK and the adjacent word lines WLK−1 and WLK+1. Accordingly, if the word line WLK is toggled between an active state and a precharge state, data stored in the memory cells CELL_K−1 and CELL_K+1 may be damaged due to a change in the amount of charge stored in the cell capacitors CAP_K−1 and CAP_K+1.
Furthermore, data stored in a memory cell may be damaged because electrons within the cell capacitor of a memory cell coupled to an adjacent to word line are introduced and drained due to an electromagnetic wave that is generated when a word line is toggled between an active state and a precharge state.